<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        section {
            width: 1000px;
            height: 400px;
            background-color: black;
            display: flex;

        }
        section div {
            flex: 1;
        }
        section div:nth-child(1) {
            background-color: red;
            flex: 2;
        }
        section div:nth-child(2) {
            background-color: yellow;

        }
        section div:nth-child(3) {
            background-color: blue;
        }
    </style>
</head>
<body>
    <section>
        <div></div>
        <div></div>
        <div></div>
    </section>
</body>
</html>